<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let sys = Symbol("cat");
        let po = Symbol("cat");
        let pos = Symbol.for("cat");
        console.log(sys);
        let cat = {
            id:"ca",
            [sys]:"ca;s"
        }
        console.log(cat);
        for (let key in cat){
            console.log(cat[key]);
        }
        console.log(Reflect.ownKeys(cat));
        console.log(sys===po);
        console.log(Symbol.for("cat")===Symbol.for("cat"));
        console.log(sys===Symbol.for("cat"));
        console.log(pos===Symbol.for("cat"));

        let call = [1,23,4,5,6,7,5,2,1,13,2,"cat","cat"];
        let newArr = [];
        let mas = {};
        [].forEach.call(call,value=>{
            mas[value] = value;
        });
        let mlk = new Proxy(mas,{
            get(target,key){
                console.log(this);
            }
        });
        console.log(Reflect.ownKeys(mlk));//["1", "2", "4", "5", "6", "7", "13", "23"]
    </script>
</body>
</html>